Transcript Watson and Crick- Structure of DNA

Watson and CrickStructure of DNA
Linnette Ostos
and Kyra Ange
James Watson's Background
~ Growing up, James Watson was a very intelligent young child.
~Later in his life, Watson finished his high school education in two years.
Once he completed his grade school, he went to the University of
Chicago.
~A quality of his which helped him towards his interest in science was his
curiosity in figuring out "why" things occur. He always wanted a
deeper understanding of the questions he tried solving.
~Watson was interested in biology and zoology.
~After Watson furthered his education by receiving his Ph.D in 1950 at
Indiana University, he spent some time in Europe.While he was in
Europe he went to the Cavendish Laboratory and the University of
Crick's Background
•
•
Earned a bachelors degree in physics from University
College London
Started research for a Ph.D. under Prof E. N. da C.
Andrade, but this was interrupted by the outbreak of war
in 1939. During the war he worked as a scientist for the
British Admiralty, mainly in connection with magnetic
and acoustic mines (Helped develop radr and magnetic
mines during World War1). He left the Admiralty in 1947
to study biology.
Watson meets Crick/
Performance
~Watson's approach to genetic research persuaded Crick to assist him in forming a DNA model.
~During this time DNA research was not a high priority for most scientists.
~Watson and Crick proceeded to develop their own hypothesis. They believed the DNA
structure was actually made of two parallel strands. They obtained structural working
models and attempted to fit the pieces together using proven chemical laws and prior
studies. Many times the model fell apart or simply did not fit previously established
evidence (it resembled a tinker- toy).
~Finally, two major clues fell into place. Watson and Crick knew that the amounts of the base
pairs of amino acids (protein elements) which connect the two strands of the DNA
molecule, were about the same size and shape. Information supplied by Maurice Wilkins
and Rosalind Elsie Franklin also suggested that the sugar-phosphate part of the structure
was on the outside of the model. Watson noticed that the base pairs fit neatly into the
overall twisted ladder or double helix form without any distortion. It also meant that each
side of the ladder fit into the other.
This explained how DNA could be precisely copied each time a cell divides. The completed
model consisted of a double backbone of sugar and phosphate molecules arranged in
repeating units. Between these, like rungs in a ladder, were the flat pairs of bases.
DNA Helix
• 2 strands of double helix are anti-parallel.
• Sugar phosphate backbone is on the
outside of the helix
• Each rung is composed of two base pairs
o Adenine and Thymine
o Cytosine and Guanine
Experiment
In 1951, Crick and Watson used the X-ray diffraction
results of Gosling and Franklin. This served as a guide
for the development of a helical structure of DNA. This is
what led them to their great contribution to the biological
field.
Importance to the Biology
Community
~The discovery of the DNA molecule by James Watson and
Francis Crick had focused the biological community's
attention on the molecular basis of life and away from
natural history and the study of species evolution. Watson
went so far as to compare natural history to stamp
collecting. Wilson knew better, and deployed advances in
microchemistry to inform the traditional practices of
natural history. Collaborating with the mathematician
William Bossert, he investigated the phenomenon of
chemical communication among ants. Wilson and Bossert
identified the chemical compounds, known as pheromones,
that permit ants and other species to communicate by
sense of smell.
Conclusion
In 1953 James Watson and Francis Crick revealed the structure and
properties of DNA, the molecule that carries our genetic information.
What they discovered was that the blueprint for a human being was
encapsulated in a long string of nucleic acid, arranged in a double
helix, like a twisted rope ladder with three billion rungs. For this
discovery Watson and Crick, together with Maurice Wilkins, were
awarded the Nobel Prize in Physiology or Medicine in 1962.
The original DNA model by Watson and Crick.
Photo:
Cold Spring Harbor Laboratory Archives
Other Points/ How other Scientist Continued
the Work of Watson and Crick
~But one big question remained unanswered: how is the information in
the DNA strand translated to protein? Among many others, three
scientists, Marshall Warren Nirenberg, Har Gobind Khorana and
Robert William Holley, set their minds on understanding how the fourletter code of DNA could be translated into the 20-letter alphabet of
amino acids, the building blocks that make up proteins.
Sources
~http://www.discoveriesinmedicine.com/General-Information-andBiographies/Watson-James-Dewey.html#b
~http://www.dnaftb.org/19/bio.html
~http://www.nobelprize.org/educational/medicine/gene-code/history.html
~http://www.nobelprize.org/educational/medicine/dna_double_helix/re
admore.html
~http://www.chemheritage.org/discover/online-resources/chemistryin-history/themes/biomolecules/dna/watson-crick-wilkins-franklin.aspx